Loneliness accelerates cognitive decline in older adults, says a research team presenting at the Alzheimer’s Association International Conference in Washington, D.C. The findings build on recent research indicating that late-life depression is linked with an increased incidence of Alzheimer’s disease.

Researchers from the Brigham and Women's Hospital and Harvard Medical School reviewed data for more than 8,300 adults age 65 and older participating in the U.S. Health and Retirement Study from 1998 to 2010. Participants in the study were assessed every two years across a range of factors, including levels of depression, loneliness, memory, cognitive function and social network status. About 1,400 of the participants (17%) reported loneliness at the start of the study, and roughly half of that group also reported clinically significant depression.

Over the 12-year study, participants reporting loneliness experienced 20% faster cognitive decline than other participants. This result held true regardless of factors like demographics, socioeconomic status and the presence of other debilitating health conditions. Higher levels of depression also correlated significantly with more rapid cognitive decline.

“Our study suggests that even one or two depressive symptoms – particularly loneliness – is associated with an increased rate of cognitive decline over 12 years,” said Nancy J. Donovan, MD, of the Brigham and Women's Hospital. “We found that lonely people decline cognitively at a faster rate than people who report more satisfying social networks and connections.”

The researchers also evaluated the possibility that reduced cognitive function might lead to greater loneliness, but didn’t find evidence to support a link in that direction.

The research adds to a growing chorus of studies pointing to loneliness as a major contributing factor in a number of mental and physiological health conditions.

“Although loneliness and depression appear closely linked, loneliness may, by itself, have effects on cognitive decline. This is important to know as we develop treatments to enhance cognitive health and quality of life for older adults,” added Donovan.

David DiSalvo is the author of "Brain Changer: How Harnessing Your Brain’s Power to Adapt Can Change Your Life" and the best-selling "What Makes Your Brain Happy and Why You Should Do the Opposite", which has been published in 13 languages. His work has appeared in Scientif...